On Mon, Mar 10, 2008 at 11:35:50AM -0700, Jeremy Fitzhardinge wrote:> Hm, given that Xen doesn't make any topology guarantees about vcpus, I > don't think it would make much difference. I think it would only be > observable if you actually pinned the vcpus to physical siblings. > Besides we could easily maintain sibling info and look to see if we're > about to reload cr3 to match the other thread(s), then just use the same > pgd copy.

The optimization doesn't really require any topology information; you just should make sure that if you have a VM shared betweendifferent CPUs that it has the same CR3. The easiest way to enforcethat is to always only use a single CR3 for a VM.